/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.solr.search.function;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Searcher;

import java.io.IOException;
import java.util.Map;

/**
 * <code>LinearFloatFunction</code> implements a linear function over another
 * {@link ValueSource}. <br>
 * Normally Used as an argument to a {@link FunctionQuery}
 * 
 * @version $Id: LinearFloatFunction.java 1065312 2011-01-30 16:08:25Z rmuir $
 */
public class LinearFloatFunction extends ValueSource {
	protected final ValueSource source;
	protected final float slope;
	protected final float intercept;

	public LinearFloatFunction(ValueSource source, float slope, float intercept) {
		this.source = source;
		this.slope = slope;
		this.intercept = intercept;
	}

	@Override
	public String description() {
		return slope + "*float(" + source.description() + ")+" + intercept;
	}

	@Override
	public DocValues getValues(Map context, IndexReader reader)
			throws IOException {
		final DocValues vals = source.getValues(context, reader);
		return new DocValues() {
			@Override
			public float floatVal(int doc) {
				return vals.floatVal(doc) * slope + intercept;
			}

			@Override
			public int intVal(int doc) {
				return (int) floatVal(doc);
			}

			@Override
			public long longVal(int doc) {
				return (long) floatVal(doc);
			}

			@Override
			public double doubleVal(int doc) {
				return (double) floatVal(doc);
			}

			@Override
			public String strVal(int doc) {
				return Float.toString(floatVal(doc));
			}

			@Override
			public String toString(int doc) {
				return slope + "*float(" + vals.toString(doc) + ")+"
						+ intercept;
			}
		};
	}

	@Override
	public void createWeight(Map context, Searcher searcher) throws IOException {
		source.createWeight(context, searcher);
	}

	@Override
	public int hashCode() {
		int h = Float.floatToIntBits(slope);
		h = (h >>> 2) | (h << 30);
		h += Float.floatToIntBits(intercept);
		h ^= (h << 14) | (h >>> 19);
		return h + source.hashCode();
	}

	@Override
	public boolean equals(Object o) {
		if (LinearFloatFunction.class != o.getClass())
			return false;
		LinearFloatFunction other = (LinearFloatFunction) o;
		return this.slope == other.slope && this.intercept == other.intercept
				&& this.source.equals(other.source);
	}
}
